Lively member joining in a student run out (7)
I believe the answer is:
allegro
'lively' is the definition.
(I've seen this before)
'member joining in a student run out' is the wordplay.
'member joining' becomes 'leg' (I can't explain this - if you can you should believe this answer much more).
'in' is an insertion indicator.
'student' becomes 'l' (as in L-plates for learner drivers).
'run out' becomes 'RO' (cricket abbreviation).
'a'+'l'+'ro'='alro'
'leg' placed within 'alro' is 'ALLEGRO'.
Can you help me to learn more?
(Other definitions for allegro that I've seen before include "In a brisk and lively manner" , "Brisk musical piece" , "A fast piece of work" , "Moving fast" , "(In music) briskly" .)